Preheat the oven to 325°F convection setting (or 350°F standard)
Spray 1 6-inch cake pan with cooking spray and a parchment paper circle, set aside
Measure the sour cream, canola oil and vanilla extract into a bowl and set aside
In the bowl of the stand mixer with the paddle attachment, mix the dry ingredients together: cake flour, sugar, baking powder and salt
With the mixer on low, add the room temperature butter in small pieces to the dry ingredient mixer. Keep the mixer running until you create a sandy texture with the butter broken up into evenly sized pieces, about 2 and half minutes.
Scrape down the bowl
With the mixer on medium, slowly pour in the liquids mixture. The batter will look lumpy at this point, keep mixing until it is evenly combined.
Scrape down the bowl, ensuring there are no clumps of flour stuck at the bottom of the bowl
Add 1 egg white and mix on low until it is fully absorbed, about 1 minute
Scrape down the bowl
Add the second egg white and mix until it is fully absorbed
Bake for 30 minutes at 325°F convection setting (or 350°F standard), until a toothpick inserted in the center comes out clean
Cool on a cooling rack for 15 minutes before removing from pan and then cool completely before frosting about 1 hour